Olefin polymers are used in a wide variety of products, from sheathing for wire and cable to film. Olefin polymers are used, for instance, in injection or compression molding applications, in extruded films or sheeting, as extrusion coatings on paper, for example photographic paper and digital recording paper, and the like. Improvements in catalysts have made it possible to better control polymerization processes and, thus, influence the properties of the bulk material. Increasingly, efforts are being made to tune the physical properties of plastics for lightness, strength, resistance to corrosion, permeability, optical properties, and the like, for particular uses. Chain length, polymer branching and functionality have a significant impact on the physical properties of the polymer. Accordingly, novel catalysts are constantly being sought in attempts to obtain a catalytic process for polymerizing olefins which permits more efficient and better-controlled polymerization of olefins.
Conventional polyolefins are prepared by a variety of polymerization techniques, including homogeneous liquid phase, gas phase, and slurry polymerization. Certain transition metal catalysts, such as those based on titanium compounds (e.g. TiCl3 or TiCl4) in combination with organoaluminum cocatalysts, are used to make linear and linear low-density polyethylenes as well as poly-α-olefins such as polypropylene. These so-called “Ziegler-Natta” catalysts are quite sensitive to oxygen and are ineffective for the copolymerization of nonpolar and polar monomers. Following the early discovery of Ziegler-Natta catalysts, there has been intense recent interest in the development and study of homogeneous early transition metal (Group 4-6) catalysts for the polymerization of olefins. These well-defined catalysts, which were first viewed as mechanistic models for heterogeneous Ziegler-Natta catalysts, are receiving increasing commercial attention. In fact, a growing understanding of the relationship between catalyst structure and polymer properties has led to significant advances in rational catalyst design. Recent advances in Group 4-6 single-site olefin polymerization catalysis include the following.
The following documents describe the use of monocyclopentadienyl amido titanium complexes for the polymerization of olefins as described by J. M. Canich, EP 420,436 (1991) and Stevens et al., EP 416,815 (1991). Waymouth et al., Science, 1995, 267, 217, disclose the use of oscillating catalysts based on unbridged substituted indenyl complexes of zirconium. Mitsui Chemicals Inc. disclose the use of nitrogen/oxygen chelate ligands on Group 4-6 transition metals as catalysts for the polymerization of olefins, EP 874,005 (1998). McConville et al., J. Am. Chem. Soc., 1996, 118, 10008-10009, describe the living polymerization of olefins with chelating diamido complexes of Ti and Zr. Schrock et al., J. Am. Chem. Soc., 1997, 119, 3830, J. Am. Chem. Soc., 1999, 121, 5797, also describe catalysts comprising chelating diamido complexes of Ti and Zr. DSM (WO 94/14854 and EP 0 532 098 A1), BP (EP 0 641 804 A2 and EP 0 816 384 A2), Chevron (WO 94/11410), and Exxon (WO 94/01471) describe the use of Group 4-6 imido catalysts for the polymerization of olefins. Jordan et al., WO 98/40421, disclose the use of novel cationic Group 13 complexes incorporating bidentate ligands as olefin polymerization catalysts.
Recent advances in Group 8-10 catalysts for the polymerization of olefins include the following.
European Patent Application No. 381,495 describes the polymerization of olefins using palladium and nickel catalysts, which contain selected bidentate phosphorous containing ligands.
U. Klabunde, U.S. Pat. Nos. 4,906,754, 4,716,205, 5,030,606, and 5,175,326, describes the conversion of ethylene to polyethylene using anionic phosphorous, oxygen donors ligated to Ni(II). The polymerization reactions were run between 25 and 100° C. with modest yields, producing linear polyethylene having a weight-average molecular weight ranging between 8K and 350 K. In addition, Klabunde describes the preparation of copolymers of ethylene and functional group containing monomers.
M. Peuckert et al., Organomet. 1983, 2(5), 594, disclose the oligomerization of ethylene using phosphine/carboxylate donors ligated to Ni(II), which showed modest catalytic activity (0.14 to 1.83 TO/s). The oligomerizations were carried out at 60 to 95° C. and 10 to 80 bar ethylene in toluene, to produce α-olefins.
R. E. Murray, U.S. Pat. Nos. 4,689,437 and 4,716,138, describes the oligomerization of ethylene using phosphine, sulfonate donors ligated to Ni(II). These complexes show catalyst activities approximately 15 times greater than those reported with phosphine, carboxylate analogs.
W. Keim et al., Angew. Chem. Int. Ed. Eng., 1981, 20, 116, and V. M. Mohring et al., Angew. Chem. Int. Ed. Eng., 1985, 24, 1001, disclose the polymerization of ethylene and the oligomerization of α-olefins with aminobis(imino)phosphorane nickel catalysts.
Wilke, Angew. Chem. Int. Ed. Engl., 1988, 27, 185, describes a nickel allyl phosphine complex for the polymerization of ethylene.
K. A. O. Starzewski et al., Angew. Chem. Int. Ed. Engl., 1987, 26, 63, and U.S. Pat. No. 4,691,036, describe a series of bis(ylide) nickel complexes, used to polymerize ethylene to provide high molecular weight linear polyethylene.
L. K. Johnson et al., WO 96/23010; U.S. Pat. No. 5,866,663; U.S. Pat. Nos. 5,886,224; 5,891,963; 5,880,323; and 5,880,241; disclose the polymerization of olefins using cationic nickel, palladium, iron, and cobalt complexes containing diimine and bisoxazoline ligands. This document also describes the polymerization of ethylene, acyclic olefins, and/or selected cyclic olefins and optionally selected unsaturated acids or esters such as acrylic acid or alkyl acrylates to provide olefin homopolymers or copolymers. L. K. Johnson et al., J. Am. Chem. Soc., 1995, 117, 6414, describe the polymerization of olefins such as ethylene, propylene, and 1-hexene using cationic α-diimine-based nickel and palladium complexes. These catalysts have been described to polymerize ethylene to high molecular weight branched polyethylene. In addition to polymerizing ethylene, the Pd complexes act as catalysts for the polymerization and copolymerization of olefins and methyl acrylate.
WO 97/02298 discloses the polymerization of olefins using a variety of neutral N, O, P, or S donor ligands, in combination with a nickel(0) compound and an acid.
Eastman Chemical Company has recently described in a series of patent applications (WO 98/40374, WO 98/37110, WO 98/47933, and WO 98/40420) several new classes of Group 8-10 transition metal catalysts for the polymerization of olefins. Also described are several new polymer compositions derived from epoxybutene and derivatives thereof.
Brown et al., WO 97/17380, WO 97/48777, WO 97/48739, and WO 97/48740, describe the use of Pd α-diimine catalysts for the polymerization of olefins including ethylene in the presence of air and water.
Fink et al., U.S. Pat. No. 4,724,273, describe the polymerization of α-olefins using aminobis(imino)phosphorane nickel catalysts and the compositions of the resulting poly(α-olefins).
Recently, Vaughan et al., WO 97/48736, Denton et al., WO 97/48742, and Sugimura et al., WO 97/38024, describe the polymerization of ethylene using silica supported α-diimine nickel catalysts.
Phillips, EP 884,331, discloses the use of nickel α-diimine catalysts for the polymerization of ethylene in their slurry loop process.
Neutral nickel catalysts for the polymerization of olefins are described in WO 98/30610; WO 98/30609; WO 98/42665; and WO 98/42664.
Highly active iron and cobalt catalysts ligated by pyridine bis(imines) for the polymerization and oligomerization of ethylene have been independently described by University of North Carolina-Chapel Hill (WO 99/02472), DuPont (WO 98/27124), BP Chemical and Imperial College (WO 99/12981).
Also recently, Canich et al., WO 97/48735, and Mecking, DE 19707236 A1, describe the use of mixed α-diimine catalysts with group IV transition metal catalysts for the polymerization of olefins. Additional recent developments are described by Sugimura et al. in JP 96-84344 and JP 96-84343, by Yorisue et al. in JP 96-70332, by McLain et al. in WO 98/03559, by Weinberg et al. in WO 98/03521, by Wang et al. in WO 99/09078, by Coughlin in WO 99/10391, and by Matsunaga et al. in WO 97/48737.
Notwithstanding these advances in non-Ziegler-Natta catalysis, there remains a need for new transition metal catalysts, particularly those which are more thermally stable, allow for new polymer microstructures, or are more functional group tolerant. In addition, there is a need for novel methods of polymerizing olefins employing such catalysts, and for the novel polymers which result.